Analog and Digital Recording/Transcript
Transcript Title text reads, The Mysteries of Life with Tim and Moby. Tim, is listening to an MP3 player with headphones. He is singing and playing air guitar. TIM: My girl wants to party all the time, party all the time, party… Moby appears, holding a letter. Moby beeps. Tim takes off his headphones, looking embarrassed. TIM: What? It's a catchy song. Moby hands Tim the letter. Text reads as Tim narrates: Dear Tim & Moby, what's the difference between an analog and digital recording? From, Xander. TIM: Analog and digital are two different ways of storing information. Analog, the older of the two technologies, is based on the electromagnet. On-screen, an electromagnet appears. It is a horseshoe-shaped magnet connected by wires to a battery. An electrical field appears around the magnet's poles. A label reads, analog. Another label reads, electromagnet. TIM: Analog media, like records and tapes, store complete sound and light waves as representations of an electric current. On-screen, a cassette tape and a vinyl record appear. A close-up view shows that the grooves on the record represent sound waves. TIM: Digital technology is based on the microchip. On-screen, a microchip appears. A label reads, digital. Another label reads, microchip. Digital media, like C-D's, hard disks, and flash memory chips, store parts of sound or light waves as 1's and 0's, or bits. On screen, a CD, a hard disk, and a flash memory recorder appear. A close-up reveals that the surface of the CD is studded with bumps. A label next to the close-up view reads, bits. Moby beeps. TIM: Um, all right. Let's get practical. Say you want to record your voice. Whether you store it on a digital or analog medium, you need something to convert the sound waves from your larynx into an electric signal. On-screen, sound waves come from Tim's mouth as he speaks. The waves strike a wire, and an electric signal travels down it. TIM: And that's what microphones are for. On-screen, a microphone appears at the end of the wire closest to Tim. TIM: Hello, this is Tim. On-screen, as Tim speaks into the microphone, another electric signal travels down the wire. TIM: In an analog device, this electric signal passes through a wire wrapped around a piece of metal containing iron. On-screen, the wire leads to a cassette recorder. A close-up view reveals the tape head, which is a curved piece of metal with wire wrapped around it. A length of magnetic tape is stretched below the tape head. TIM: As current passes through the wire, the metal becomes an electromagnet. On-screen, an electric signal passes through the wire and around the tape head, creating a magnetic field. The magnetic tape scrolls slowly past the tape head. The previous image of the electromagnet appears below the tape recorder. Moby beeps. TIM: That's called electrical induction; electricity induces a magnetic field in the metal. Changes in the electric signal result in changes to the magnetic field. On-screen, the signal in the wire gets stronger, and the magnetic field coming from the tape head grows larger. A label reads, electrical induction. TIM: These changes are recorded as a pattern onto analog media, like magnetic tape, or a wax record. On-screen, the magnetic tape changes as it passes the tape head. Before passing the tape head, iron particles in the magnetic tape are arranged in all different directions. After passing the tape head, the particles are arranged in an orderly pattern. TIM: When you play the tape or record, the playing device converts the pattern back into a signal. The signal is sent to a speaker, where it comes out as sound. On-screen, a wire connects the cassette player to a speaker. An electric signal travels along the wire, and sound waves come out of the speaker as it plays a recording of Tim's voice saying, Hello, this is Tim. TIM: All analog devices work by this same principle: electromagnets make a representation of a sound or light wave! On-screen, sounds waves strike an ear. Moby beeps. TIM: Digital is a different story. On-screen, Tim speaks into the microphone again. TIM: Hello, this is Tim. On-screen, the microphone catches the sound waves. An electric signal moves down the microphone's wire to a desktop computer. TIM: In a digital device, an electric signal goes to something called an analog-to-digital converter, or A, D, C. On-screen, the signal travels to a chip inside the computer. A label reading, analog-to-digital converter, appears. TIM: The A, D, C, analyzes the signal, and takes samples of it. On-screen, the A, D, C, beeps rapidly as it processes the electrical signal. Moby beeps. TIM: Well, analog devices record an entire wave. That means you're sure to get a true reproduction of sound, but the storage space required is enormous. On-screen, a wavy line representing a sound wave appears above a tape head and a piece of magnetic tape. Many cassette tapes appear next to the wave. A label reads, analog. TIM: Digital devices record millions of pieces, or samples, of that wave. On-screen, the tape deck is replaced by an A, D, C, and the smooth sound wave is replaced by a jagged one. A label reads, digital. TIM: Recording pieces requires less space than recording the whole. On-screen, a comparison shows that two C-D's can hold the same amount of information as a large number of cassette tapes. TIM: Well, it's like if you draw a face with lines. And then draw one made up of dots close together. On-screen, a simple drawing of a face appears. A similar face, drawn with dots instead of lines, appears next to it. TIM: The dot drawing uses less ink, and, from a distance, they look the same. Your brain fills in the missing information. The more samples taken per second, the more similarity, or fidelity, the digital wave will have to the original wave. On-screen, a smooth sound wave appears next to the jagged one. The jagged wave becomes less jagged, matching the smooth wave more closely. A label reading, fidelity, appears. TIM: This is called sampling frequency. A label appears, reading, sampling frequency. TIM: Each sample's amplitude, the height of the sound wave, is described by a number. On-screen, a ruler measures the height of each section of the jagged wave. The ruler measures from 0 to 5. A label reads, amplitude. TIM: The more numbers available to describe the amplitude, the higher the sampling precision. On-screen, the ruler now measures from 0 to 10. A label reads, sampling precision. TIM: You can think of sampling precision like a paint set; the more colors you have in the set, the more realistic your paintings can be. On-screen, the simple drawing of the face appears. It includes only two colors. Next to it, another face appears, drawn with shading and more colors. TIM: The analog-digital converter converts the stream of samples into 1's and 0's. On-screen, an electric signal enters the A, D, C. It beeps rapidly with each electric pulse. TIM: These are coded onto a medium like a CD or hard disk. On-screen, a CD and a disc drive appear. TIM: To change the ones and zeros back into an electric signal, digital playback devices use a digital-to-analog converter, or D, A, C. On-screen, a desktop computer appears. A view inside the computer shows an electric signal traveling to a microchip, marked D, A, C. The signal leaves the chip, and travels down a wire to the computer’s speaker. Sound waves come out of the speaker as it plays a recording of Tim's voice saying, Hello, this is Tim. Moby beeps. TIM: Well, there are a couple of advantages to digital. First of all, the file itself doesn't deteriorate; you can make infinite copies without losing any information! Plus, you can fit more data onto smaller devices. On-screen, a large, vinyl record appears next to a much smaller CD. TIM: Digital data can also be compressed, or shrunk down even further! On-screen, an even smaller CD appears next to the first CD. TIM: But some people say that analog media just looks and sounds better than digital. On-screen, a smiling man with a goatee and beret listens to an old-fashioned record player. TIM: And things like C-Ds have a relatively short life span, especially if they were blank C-Ds to begin with. After as few as 2 years, some C-Ds will just stop playing properly. Moby and Tim listen to a song playing off-screen. It skips, then stops playing. TIM: So you have to copy or back up your files to ensure that they will last, which can be a royal pain if, say, you have a big music collection. A label appears, reading, back up. TIM: I guess it all just depends on what you're looking for, or what you're listening for! Moby is now wearing headphones. TIM: So, what are you listening to? Moby gives Tim his headphones. He beeps. Tim puts the headphones on. He hears the sound of an old dial-up modem. TIM: Hmm. Category:BrainPOP Transcripts